try to put your samples at 0 C for 1 hour or more(RNA is stable in formamide) than to centrifugate at 16000 g (4 C) for 10-15 min, and remove the supernatant - pellet should be your rna. To visualize pellet you can add some GlycoBlue (Ambion) to your sample before everything (it also important if working with small amounts of rna). I used to do it with 80% formamide - think it would work in your case, otherwise - just add TE buffer to your samples to make it 80% formamide))